Gas generation dispenser apparatus for on-demand fluid delivery

ABSTRACT

An on-demand fluid dispenser to dispense fluid in response to gas generation by a gas cell. The on-demand fluid dispenser includes an expandable gas chamber, a fluid chamber, and an on-demand gas cell. The expandable gas chamber includes a moveable plunger forming a wall of the expandable gas chamber. The moveable plunger also forms a wall of the fluid chamber. The on-demand gas cell is configured to generate the gas on demand. The on-demand gas cell is also configured to direct the gas to the expandable gas chamber to expand the expandable gas chamber. Expansion of the expandable gas chamber moves the moveable plunger to reduce a volume of the fluid chamber and to dispense an amount of fluid from the fluid chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of, and claims priority to, U.S.application Ser. No. 11/923,490, filed Oct. 24, 2007, which claimedpriority U.S. Provisional Patent Application No. 60/912,463, filed onApr. 18, 2007. Both of these applications are incorporated by referenceherein in their entirety.

BACKGROUND

Dispensing devices such as those that periodically deliver a shot offragrance into the air are well known. These devices have variouscontrol and activation systems including batteries and timers. Themechanisms for delivering the shot may include aerosol type devices thatoperate over a large range of pressures and piezo pumps.

Conventional gas cells are used for generating gases such as hydrogenfrom liquids such as water at relatively slow rates in which a volume ofgas is generated slowly for periodic use of the gas for motive or otherpurposes. These gas cells are used in fluid delivery systems thatoperate automatically. For example, some conventional gas cells in fluiddelivery systems continuously generate gas at a slow rate over a longperiod of time. A build-up in pressure provides a motive force forcausing the fluid to exit from a storage chamber. The force is typicallyautomatically applied at predetermined time intervals under the controlof a timer and other controls for automatic, periodic delivery of thefluid.

Conventional fluid delivery systems that utilize gas cells are deficientin accounting for changes in environmental or system conditions. Forexample, as a volume of a gas chamber in a conventional fluid deliverysystem increases over time, the generation of the gas at a constant ratehas a changing effect on the fluid delivery over time due to changes inatmospheric pressure, temperature, or other environmental conditions.Changes in pressure of contained gas due to changes in temperature orelevation typically impact the amount of fluid delivered by conventionalgas generation fluid delivery systems such that these systems lackconsistency under changing operating conditions.

SUMMARY

In one embodiment, a method of dispensing a fluid includes generating agas from a liquid. The method also includes directing the gas to anexpandable gas chamber to expand a volume of the expandable gas chamber.The method includes reducing a volume of a fluid chamber in response toexpansion of the expandable gas chamber to dispense an amount of thefluid from the fluid chamber. The method also includes removing the gasfrom the expandable gas chamber to collapse the expandable gas chamber.Other embodiments of the method are also described.

In one embodiment, an on-demand fluid dispenser includes an expandablegas chamber. The expandable gas chamber includes a moveable plungerforming a wall of the expandable gas chamber. The moveable plunger alsoforms a wall of the fluid chamber. An on-demand gas cell is configuredto generate the gas on demand and to direct the gas to the expandablegas chamber to expand the expandable gas chamber. In this case,expansion of the expandable gas chamber moves the moveable plunger toreduce a volume of the fluid chamber and to dispense an amount of fluidfrom the fluid chamber. Additionally, a power source may be connected tothe gas cell, and a switch may be coupled to the power source toactivate the gas cell. Other embodiments of the on-demand fluiddispenser are also described.

Other aspects and advantages of embodiments of the present inventionwill become apparent from the following detailed description, taken inconjunction with the accompanying drawings, which are illustrated by wayof example of the various principles and embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary perspective view of one embodiment of anon-demand fluid dispenser.

FIG. 2 is a diagrammatic sectional view of another embodiment of anon-demand fluid dispenser.

FIG. 3 is a schematic diagram of one embodiment of an electrical circuitthat may be incorporated in an embodiment of the on-demand fluiddispenser.

FIGS. 4A-4C are diagrammatic partial sectional views illustrating anembodiment of a process for dispensing fluid from an on-demand fluiddispenser.

FIGS. 5A-5J are detailed views of the indicated regions in FIG. 4Billustrating examples of alternative mechanisms for inhibiting movementof an element of the on-demand fluid dispenser in one direction relativeto another element of the dispenser.

FIGS. 6A-6C are diagrammatic sectional views of a variety ofcombinations of elements and methods that may be implemented inembodiments of the on-demand fluid dispenser.

FIG. 7 is a diagrammatic sectional view of a piezo valve that may beincorporated in embodiments of the on-demand fluid dispenser.

Throughout the description, similar reference numbers may be used toidentify similar elements.

DETAILED DESCRIPTION

In the following description, specific details of various embodimentsare provided. However, some embodiments may be practiced with less thanall of these specific details. In other instances, certain methods,procedures, components, structures, and/or functions are described in nomore detail than to enable the various embodiments of the invention, forthe sake of brevity and clarity. It is to be understood that thefeatures shown and described with regard to the various embodiments maybe combined by adding or substituting in any combination withoutlimitation.

FIG. 1 is an exemplary perspective view of one embodiment of anon-demand fluid dispenser 10. It is to be understood that the term“dispenser” is generally used herein to describe embodiments of theon-demand fluid dispensers, and the terms “dispenser” and “on-demandfluid dispenser” are used interchangeably, in many instances. However,some embodiments of the dispenser may be implemented without theon-demand capability while maintaining other characteristics ofembodiments described herein.

In the depicted embodiment, a user 15 may grasp the dispenser 10 in anycomfortable manner In FIG. 1, a syringe type of grip is illustrated,although other grips may be used depending on the configuration of theon-demand fluid dispenser 10. A button 20 may be located on alongitudinal end or on a side of the dispenser 10 without loss ofmeaning or functionality. As shown, the user 15 may press the button 20to actuate the dispenser 10, and dispense a fluid 25 in accordance withat least some of the details described herein. With a gas generationmechanism and mechanisms for inhibiting the impact of variations inconditions in the environment and in the conditions in the dispensersystem itself (referred to collectively herein as operating conditions),a reliable dispenser 10 is made possible.

FIG. 2 is a diagrammatic sectional view of another embodiment of anon-demand fluid dispenser 30. The dispenser 30 may include at least someof the features and characteristics that are presented in the U.S.Provisional Patent Application Ser. No. 60/912,463, filed Apr. 18, 2007,which is incorporated herein by reference. As shown, the dispenser 30has a housing 33 and a button 20 similar to the button 20 shown inFIG. 1. The button 20 may be urged away from leads 36 by a resilientelement 39. The leads 36 are connected to a printed circuit board orother substrate 42, which may support an electronic controller(described below) for the dispenser 30. A battery or other power source45 is connected to the substrate 42 for providing power to the dispenser30 through operation of the electronic controller in response to aninput signal when the user presses the button 20. In one embodiment, thebutton 20 and leads 36 form part of a momentary switch that includes atimer so that pressing the switch for any length of time results in apredetermined actuation time. Alternatively, the switch may be acontinuous switch that actuates the dispenser 20 continuously for aslong as the user 15 actuates the switch.

In one embodiment, the electronic controller delivers power to a gascell 48, which then produces gas 50 from a liquid (not shown in FIG. 2).The gas 50 is directed into an expandable gas chamber 51. The pressureof the gas 50 causes the expandable gas chamber 51 to expand. As aresult, a plunger or first movable wall 54 moves away from the gas cell48 and toward a front end of the dispenser 30 by the increased pressureof the gas 50 in the expandable gas chamber 51. As the plunger 54 movesaway from the gas cell 48 within the dispenser 30, the plunger wall 54reduces a volume in a fluid chamber 57. In the embodiment illustrated inFIG. 2, a flexible bag 60 containing a fluid 63 to be dispensed ispositioned in the fluid chamber 57. Thus, when the plunger 54 movesforward, it compresses the bag 60 and displaces an amount of the fluid63 out through an outlet 66 in a direction of arrow 67.

Some embodiments of the dispenser 30 include a mechanism for reducing animpact of operating conditions. Some exemplary mechanisms are describedherein. Environmental changes such as changes in temperature orelevation may cause changes in operating conditions such as a pressureor a volume of an enclosed chamber. Changes in ambient pressure affectthe pressure differential between an interior of a chamber and anexterior of the chamber. Thus, environmental changes have the effect ofcausing changes in rates of flow of gases and liquids within thedispenser 30. Hence, without a mechanism for reducing the impact of theoperating conditions of the dispenser 30, inconsistencies in the amountof dispensed fluid would likely be caused by changes in the environment.The mechanism for reducing the impact of these operating conditionsgenerally controls flow based on pressures such that variations in theoperating conditions are inhibited from affecting the amount of thefluid dispensed.

The dispenser 30 may include a removable cover 75 for engaging an end ofthe bag 60 around the outlet 66. The bag may have a front end plate 78of a relatively stiff material. The front end plate 78 may act as a stopfor engaging the cover 75. In an alternative embodiment, a fluid to bedispensed may be placed directly in the fluid chamber 57 without aflexible bag to contain the fluid. However, the configuration shown inFIG. 2 facilitates replacement of a fluid in the dispenser 30 since thecover 75 can easily be removed, for example, to remove an empty bag andto position a full bag for continued use. These features may be appliedsingly or together in any combination with other embodiments disclosedherein without limitation.

FIG. 3 is a schematic diagram of one embodiment of an electrical circuit81 that may be incorporated in an embodiment of the on-demand fluiddispenser 30. With reference to FIG. 3, an electronic controller mayinclude a simple circuit 81 having a switch 84 that includes the leads36, power source 45, and a capacitor 87. When the button 20 is pressed,it closes the circuit 81 and actuates the dispenser 30 in which thecircuit 81 is disposed. When activated, an electrical potential isformed across anode 90 and cathode 93. In one embodiment, the anode 90and cathode 93 engage opposite surfaces of an electrolyte membrane 96.The electrolyte membrane 96 can have liquid such as water therein and isformed of a material that facilitates electrolytic activity. Thematerial may include one or more of a variety of water-absorbentpolymeric materials including, but not limited to, NAFION® (a DuPontregistered trademark) for example. Other embodiments may use other typesof materials, including micro-porous materials, ion-exchange materials,and non-woven polymer materials. The electrodes 90, 93 may be formed ofa metallic wool or mesh material including one or more of a variety ofmaterials including, but not limited to, platinum and platinum coatedmaterials. The membrane 96 and/or the electrodes may have large surfaceareas. As such, a relatively large current is set up across theelectrolyte membrane 96. The power source 45 is sufficient to set up acurrent that will transfer energy to the water molecules at interfacesbetween the electrodes 90, 93 and the electrolyte membrane 96. The watermolecules subsequently separate into hydrogen and oxygen molecules thatare in a gas state and form the gas 50, as described with regard toFIG. 1. Other, more specialized, electronic controllers may besubstituted for the electronic controller implemented by circuit 81. Forexample, controllers with timers, sensors, memory, and adjustablesettings may be implemented.

FIGS. 4A-4C are diagrammatic partial sectional views illustrating anembodiment of a process for dispensing fluid from an on-demand fluiddispenser 30. FIGS. 4A-4C show respective operations of the process thatis included with at least some of the apparatuses and methods describedherein. For example, FIG. 4A shows the first movable wall 54 (i.e., theplunger) near a second movable wall 102. The second movable wall 102 maybe termed a follower, and may be formed at least in part by one or bothof the gas cell 48 and the substrate 42. Alternatively, anotherstructure may be used to form the follower 102. The movable walls 54,102 seal the chambers on respective opposite sides of the first movablewall 54. In FIG. 4A, the movable walls 54, 102 are in close proximity toeach other with little or no gas between them such that the expandablegas chamber 51 has a relatively small volume. When the dispenser 30 isactuated and the gas 50 is generated by the gas generation cell 48, thepressure between the movable walls 54, 102 increases and applies a forceto the walls 54, 102 in opposite directions away from each other. Thesecond movable wall 102 is inhibited from movement away from the firstmovable wall 54 by any of a variety of mechanisms that are describedbelow. Thus, as shown in FIG. 4B, the first movable wall 54 is caused tomove away from the second movable wall 102 in a forward direction 105toward the fluid chamber 57. When the gas 50 is removed or permitted toescape from the expandable gas chamber 51, the movable walls 54, 102 areeither passively urged to move toward each other, for example, byambient pressure or actively urged together, for example, by a spring orpump. Additionally, the first movable wall 54 is also inhibited frommovement toward the second movable wall 102, in a backward directionthat is away from the fluid chamber 57, by any of a variety ofmechanisms that are described below. Therefore, the second movable wall102 is drawn toward the first movable wall 54 as indicated by arrow 108in FIG. 4C. The operations shown in FIGS. 4A-4C may be repeated in aniterative manner so that the movable walls 54, 102 move forward one at atime (to the right as viewed in FIGS. 4A-4C). In this way, the movementof the walls 54, 102 is one-way, or unidirectional, in the forwarddirection.

As shown in FIGS. 2 and 4A-4C, the dispenser 30 includes an outlet valve111 in the outlet 66. This valve 111 may be a one-way valve or checkvalve that allows passage of the fluid 63 out of the fluid chamber 57and inhibits backflow of the fluid 63 or air into the fluid chamber 57.Since air and other fluid cannot enter the fluid chamber 57 through theoutlet 66, a hydrostatic condition is created in which chamber 57 isheld at generally constant volume between iterations of movement of thefirst movable wall 54. Thus, the valve 111 provides a mechanism thatinhibits movement of the first movable wall 54 in a backward direction.Similarly, a one-way gas chamber valve 114 may be provided through thesecond movable wall 102. The one-way gas chamber valve 114 may be apressure sensitive valve such that when gas is being generated, thepressure sensitive one-way gas chamber valve 114 inhibits passage of thegas out through the second movable wall 102. When the gas has expanded avolume of the expandable gas chamber 51 and the pressure in theexpandable gas chamber 51 has dropped below a predetermined threshold,then the one-way gas chamber valve 114 may be automatically opened toallow passage of the produced gas out through the second movable wall102. As may be appreciated, by providing a sealed enclosure on abackward side of the second movable wall 102, a balance of the pressureson opposite sides of the second movable wall 102 may provide a mechanismthat inhibits movement of the second movable wall 102 in a backwarddirection when the valve 114 is closed. Alternatively, one or moreone-way valves in one or more of the first movable wall 54 and sidewalls of the housing 33 may be substituted for the one-way gas chambervalve 114. For example, the valve 114 may be a manually activated valveor an automatic electrically activated valve, such as a solenoid valveor a piezo valve that are described in greater detail below. Also, thevalve 114 may be another kind of valve.

FIGS. 5A-5J are detailed views of the indicated regions in FIG. 4Billustrating examples of alternative mechanisms for inhibiting movementof an element of the on-demand fluid dispenser 30 in one directionrelative to another element of the dispenser 30. FIGS. 5A and 5B aredetailed diagrammatic sectional views of exemplary structures that maybe applied in the indicated regions of FIG. 4B. The exemplary structuresmay be applied to either or both of the movable walls 54 and 102 and/orcorresponding portions of an inner surface of the housing 33. FIG. 5Ashows a pawl and ratchet mechanism for inhibiting movement of the firstor second movable wall(s) 54, 102 relative to the housing 33. Thus, apawl 117 may be pivotally supported on the movable wall(s) 54, 102 and aset of teeth 118 may be provided on the inner surface of the housing 33.The angle of the pawl 117 and teeth 118, and their relative spacing, maybe such that movement of the movable wall(s) 54, 102 is enabled in aforward direction 121 and inhibited in a backward direction relative tothe housing 33. Thus, the mechanism is a mechanism for causingunidirectional progression of the movable wall(s) 54, 102. An o-ring 124of a resilient material may be additionally provided to form a sealbetween the movable member(s) 54, 102 and the housing 33. Alternatively,a flange 125 may be provided by itself, as shown in the detailed view ofFIG. 5B. The flange 125 may have a height and flexibility that enablesthe flange 125 to be bent and lie nicely in one direction when engagedby an inner surface of the housing 33. The flange 125 creates a seal andenables movement of the movable member(s) or wall(s) 54, 102 to which itis applied in the forward direction 121. On the other hand, the flange125 may resist bending in the other direction. Thus, a force in anopposite backward direction will cause a wedging effect of the flangebetween the movable wall(s) 54, 102 and the inner surface of the housing33. Thus, a radial force and friction is increased and movement of themovable member(s) 54, 102 in the backward direction is inhibited. As maybe appreciated, the o-ring 124 and flange 125 are interchangeable as totheir sealing function. The flange 125 may be formed integrally as onepiece with the movable wall(s) 54, 102, or may be added onto the movablewall(s) 54, 102.

Alternatively, details for the indicated regions of FIG. 4B may beapplied in accordance with any of FIGS. 5C-5F to provide othermechanisms for causing unidirectional progression. As shown in thediagrammatic sectional view of FIG. 5C, a shaped o-ring 224 may beconfigured with a structure to resist movement in the backward directionwhen engaged with the teeth 118. The material of the shaped o-ring 224may be elastomeric such that the shaped o-ring 224 forms a seal andresists backward movement at the same time. In another alternative shownin FIG. 5D, torsion springs 227 may be supported on the movable wall 54,102 and engage the teeth 118 with a force in a direction 230 to inhibitbackward movement of the movable wall(s) 54, 102. An o-ring 124 may beheld in a groove 233 and form a seal similar to the o-ring 124 of theembodiment shown in FIG. 5A. Further alternatively, flexible fins 236may be integrally molded with the movable wall(s) 54, 102, as is shownin FIG. 5E. These flexible fins 236 may be angled to engage the teeth118 to inhibit movement in the backward direction, but to allow forwardmovement of the fins 236 and the movable wall(s) 54, 102. FIG. 5F showsa further alternative embodiment in which a sleeve 239 of rubber orother flexible material may be supported on an outer surface of themovable wall(s) 54, 102. The sleeve 239 may have one or more flanges 242that function to seal and inhibit movement of the movable wall(s) 54,102 in the backward direction while allowing movement of the wall(s) 54,102 in the forward direction. The sleeve 239 may be glued or vulcanizedonto the outer surface of the movable wall(s) 54, 102.

In another embodiment, FIGS. 5G-5H show diagrammatic sectional views ofmechanisms for causing unidirectional progression of the movable wall(s)54, 102 that may be incorporated in place of any of the embodimentsshown in FIGS. 5A-5F, as applied to the indicated regions of FIG. 4BLike the previously described embodiments, the mechanisms of FIGS. 5G-5Jare configured to cause sealing of the movable walls 54, 102 about theiredges relative to the inner surface of the housing 33. For example, inFIG. 5G, the movable wall(s) 54, 102 have a tapered groove 245 in anouter edge. A flexible wedge ring 248 is received in the groove 245. Asa force is applied to the movable wall(s) 54, 102 in a direction ofarrow 251, the movable wall(s) 54, 102 are moved so that a deeper end ofthe tapered groove 245 receives the wedge ring 248. Alternativelystated, the wedge ring 248 travels relative to the movable wall(s) 54,102 along a bottom of the tapered groove 245 in a direction of arrow254. Since the diameter of the tapered groove 245 decreases in adirection of the arrow 254, the wedge ring 248 is permitted to contractslightly in a radially inward direction such that flanges or ribs 257are compressed only slightly to maintain a seal between the movablewall(s) 54, 102 and the housing 33. With the wedge ring 248 in theposition shown in FIG. 5G, the movable wall is permitted to move in aforward direction corresponding to the direction of arrow 251 whilemaintaining the seal. Movement of the movable wall(s) 54, 102 in thedirection of arrow 251 may occur when, for example, a generated gasexpands the expandable gas chamber 51 and pushes movable wall 54 or whena spring urges movable wall 102 toward the movable wall 54 to contractthe expandable gas chamber 51. However, when a force acts in a backwarddirection as indicated by arrow 260 in FIG. 5H, the movable wall(s) 54,102 move back slightly such that a shallow end of the tapered groove 245causes the wedge ring 248 to stretch radially outward and more firmlyengage the inner surface of the housing 33. Alternatively stated, thewedge ring 248 travels relative to the movable wall 54, 102 in adirection of the arrow 263. In this position (shown in FIG. 5H) theflanges or ribs 257 are deformed and the contact between the ribs 257and the inner surface of the housing 33 is increased. Thus, frictionbetween the wedge ring 248 and the housing 33 is increased and movementof the wedge ring 248 and the movable wall(s) 54, 102 in a backwarddirection is inhibited. As may be appreciated, repeated iterations offorces in the forward and backward directions on the movable wall(s) 54,102 will cause generally incremental forward movement of the movablewalls 54, 102 while inhibiting all but slight movement in the backwarddirection.

FIGS. 5I and 5J are diagrammatic section views of details of a mechanismthat functions similarly to those shown and described with regard toFIGS. 5G and 5H. These details may be alternatively applied to theindicated regions of FIG. 4B. A primary difference in the mechanism ofFIGS. 5I and 5H is that it has an o-ring 124 instead of the wedge ring248 shown in FIGS. 5G and 5H. Otherwise, the structure and function ofthe mechanism for causing unidirectional movement of FIGS. 5I and 5J issubstantially similar to that of FIGS. 5G and 5H. However, FIG. 5I showsa force in the backward direction 266, which would initially be appliedto the follower or second movable wall 102 during expansion of the gasin the expandable gas chamber 51. In this position, the tapered groove245 has been moved slightly backward until the o-ring 124 is stretchedand pressed such that it grips the inner surface of the housing 33sufficiently to stop or lock the o-ring 124 and movable wall 102 againstfurther backward movement. The same locking occurs when applied to thefirst movable wall 54 during a contraction of the expandable gas chamber51, for example. As shown in FIG. 5J, in a subsequent operation when themovable wall(s) 54, 102 have a force applied in the forward direction269, a deep end of the tapered groove 245 is moved over the o-ring 124,permitting the o-ring 124 to contract and reduce its frictionalengagement with the inner surface of the housing 33. In the positionshown in FIG. 5J, the o-ring 124 forms a seal between the movablewall(s) 54, 102 and the housing 33 while permitting sliding movement ofthe o-ring 124 and movable wall(s) 54, 102 in the forward direction.

FIGS. 6A-6C are diagrammatic sectional views of a variety ofcombinations of elements and methods that may be implemented inembodiments of the on-demand fluid dispenser 30. The dispensers 30 ofFIGS. 6A-6C show a variety of elements that may be applied to anyembodiment of the dispenser 30 without limitation. For example, FIG. 6Ashows a permeable region 127 which may be integral with or added ontoone or more of the movable walls 54, 102 and a sidewall of the dispenser30. It is to be understood that the housing 33 itself could be formed ofthe permeable material, or a long strip of permeable material forming apermeable region 127 shown in dashed lines in FIG. 6A may be providedalong a length of the housing 33. The permeable region 127 may include amaterial such as polypropylene or some other material that is permeableto the gas that is being generated, for example oxygen or hydrogen gas,yet relatively impermeable to the source liquid. However, thepermeability is such that pressure builds up quickly during generationof the gas and then slowly dissipates as the gas molecules escapethrough the permeable material. After expansion during gas generation,the expandable gas chamber 51 will collapse as the pressure drops andsubstantially equalizes to the ambient air pressure outside the housing33. Collapse of the expandable gas chamber 51 may be speeded by a pumpand/or spring. The outlet 66 may have the outlet valve 111 describedabove. The walls may have additional valves and/or mechanisms forinhibiting movement of the movable walls 54, 102 in a backward directionas described above. As shown in FIGS. 6A-6C, the walls 54, 102 will moveone after another in a forward direction to the right as indicated bythe arrows 130, 131. The dashed arrows 133, 134 indicate that inaccordance with some embodiments the movable walls 54, 102 may be movedin a backward direction when the dispenser 30 is being reset andrefilled.

FIG. 6B shows the dispenser 30 with a pump 137 for actively removing thegas after it has been generated and expanded the expandable gas chamber51. The pump 137 may be incorporated together with a valve or apermeable region on any of the walls forming the expandable gas chamber51. The pump 137 may be a manually or electrically powered pump. In anycase, the pump 137 speeds removal of the gas and contributes to thefrequency with which the on-demand activation of the dispenser 30 may beeffectuated. In the embodiment of FIG. 6B, no valve is shown on theoutlet 66. A valve 111 may not be needed when the fluid being dispensedfrom the fluid chamber 57 is highly viscous, for example. On the otherhand, a valve 111 may be included in the outlet 66 without limitation.

FIG. 6C shows the dispenser 30 with a solenoid valve or other gasrelease mechanism 140 on the second movable wall 102 for releasing gasfrom an interior to an exterior of the expandable gas chamber 51. Thegas release mechanism 140 could alternatively be located on a sidewallof the housing 33 in a portion of the housing corresponding to theexpandable gas chamber 51 or any of the walls forming the expandable gaschamber 51. The gas release mechanism 140 may include a valve such asvalve 114 shown in FIGS. 4A-4C. The gas release mechanism 140 may beoperated to release the gas after it has been generated and after it hasexpanded the expandable gas chamber 51. The gas release mechanism 140may alternatively include an ionic transport pump that is anelectrochemical solid state ionic transport gas pump that has no movingparts. Further alternatively, the gas release mechanism may include anelectrochemical liquid generator to convert the gas in the expandablegas chamber 51 back into a liquid in response to the operation ofdispensing the amount of fluid from the fluid chamber 57. The convertedliquid may be stored in a liquid storage reserve (not shown) forregeneration of a gas from the converted liquid. The on-demand fluiddispenser 30 may thus convert the gas back into a liquid for reuse in agas cell generator to generate additional gas in a repeating cycle byutilizing an electrochemical reaction of chemical components within thegas. In any case, the methods may include dispensing in response to auser input for on-demand dispensing.

As shown in FIG. 6C, instead of a pump, one or more springs or otherresilient biasing element 143 may be connected to the movable walls 54,102 to draw them together. It is to be understood that such biasingelements 143 may be used in conjunction with a permeable region or avalve in any of the walls forming the expandable gas chamber 51. Aproximity switch (not shown) may be incorporated in the movable wallssuch that a valve may be automatically opened when a predeterminedamount of gas has been generated and has expanded the expandable gaschamber 51 to a predetermined volume at which the walls are sufficientlyseparated to activate the proximity switch. The resilient biasingelement(s) 143 may be replaced by magnetic elements in the form ofpermanent magnets or electromagnetic coils mounted in or on the movablewalls 54, 102. The magnetic elements may exert attractive forces on eachother such that the movable walls are drawn together. In someembodiments, the resilient biasing element(s) 143 or magnetic elementsmay be applied in a manner that they push the second movable wall 102instead of pulling it. The magnetic and/or electromagnetic forces can beactively or passively applied to collapse the expandable gas chamber. Asdepicted in FIG. 6C, the outlet 66 may alternatively include a duckbillvalve 146.

FIG. 7 is a diagrammatic sectional view of a piezo valve 272 that may beincorporated in embodiments of the on-demand fluid dispenser 30. Thepiezo valve 272 may be provided in addition to any of the gas releasemechanisms 127, 137, 140 of FIGS. 6A-6C. These gas release mechanismsgenerally include some kind of valve or opening located in a wall forreleasing a gas through the wall. For example, the valve 114 shown inFIGS. 4A-4C extends through a wall of the gas cell 48, which may atleast form part of the second movable wall 102. Alternatively, the valve114 may form an opening through the substrate 42, which may at leastform part of the second movable wall 102. The valve 114 may take theform of a solenoid valve or the piezo valve 272 shown in FIG. 7. Thepiezo valve 272 may include a piezo element 275 electrically connectedto a power source such as power source 45 by an electronic controller orswitch. An opening 278 through the second movable wall 102 (or anotherwall) may have a valve seat 281 connected in surrounding sealingrelation to the opening 278. Thus, when the piezo element 275 isenergized, it is shortened as shown in solid lines. The energizedshortened condition allows passage of gas as indicated by arrows 284.When it is de-energized, the piezo element 275 lengthens and engages thevalve seat 281, as shown by dashed lines 287 in FIG. 7. Thus, the piezovalve 272 may be opened and closed by energizing and de-energizing thepiezo element.

In one aspect, embodiments of the on-line fluid dispenser or method ofdispensing a fluid provide a balance between collapsing the expandablegas chamber while substantially maintaining the volume of the fluidchamber. That is, the mechanism for collapsing the expandable gaschamber does not also cause the fluid chamber to collapse. Rather, afterthe expandable gas chamber has been collapsed, generation of gas causesthe fluid chamber to at least partially compress.

In another aspect of embodiments of the method of dispensing a liquid,generating gas includes generating the gas at a gas generation rate thatis higher than a gas removal rate during the operation of removing thegas from the expandable gas chamber. This aspect enables the dispensersand methods in accordance with certain embodiments to be “on-demand.”

It is to be understood that this on-demand feature may be combined witha continuous gas generation mechanism that continuously generates areserve of the gas. In this embodiment, the rapid generation of gas actsin an additive manner to provide a bolus effect of delivering fluidautomatically and periodically by the continuous gas generationmechanism, and delivering fluid on-demand as a user activates thedispenser.

In the on-demand aspect of the embodiments described herein, theoperation of generating may include generating a volume of gas in afirst range from about one to one hundred microliters for a singledelivery of fluid from the fluid chamber for a single delivery of fluidfrom the fluid chamber. Alternatively, generating the gas may includegenerating a volume of gas in a range from approximately twenty toapproximately fifty microliters for the single delivery, which may takeplace over a period of approximately three seconds. A volume in theseranges may be generated in a range from one to six seconds. The periodof generation could be any number within this range, such as fiveseconds. Even with a very small easily portable dispenser, the methodmay include dispensing the fluid between about one hundred and fiftythousand times. Alternatively, the method may include dispensing fluidbetween about four thousand and fifteen thousand times from thedispenser 30. In other words, the dispenser 30 may dispense fluid asubstantial number of times potentially using a single liquid sourceand/or fluid source. In this regard, dispensing may include generatingthe gas to repeatedly dispense the amount of the fluid at substantiallyregular, discrete intervals such as by a momentary switch.Alternatively, the method may include generating gas continuously suchas by depressing a continuous switch. In any case, generating the gas todispense the fluid on demand may be in response to a user input.

The on-demand dispensing apparatus and method provides long life overmany iterations and/or plural refills. In one aspect, the apparatus andmethod enables easy portability through compactness. In another aspect,the apparatus and method is capable of consistently delivering adetermined amount of a fluid in a variety of environmental or systemconditions.

The on-demand dispensing apparatus and method in accordance with thedisclosed embodiments may be utilized in a wide variety of applicationsand environments. The fluids that can be dispensed by the dispensingapparatus and method are limitless. For example, the dispensersdisclosed herein may receive fragrances or other fluids in their fluidchambers for dispensing. By way of further example, the dispensers maybe used to dispense “beneficial agents” such as medicaments andpharmaceutical agents.

The dispenser may be a unitary device supported in a housing thatincludes the expandable gas chamber, the fluid chamber, the powersource, and the switch. The housing may be cylindrical, and have one ormore resilient member or element configured to move the second moveablewall in a single direction along a substantially linear path to collapsethe expandable gas chamber in response to the amount of fluid beingdispensed from the fluid chamber. The movable walls may be in the formof movable plungers each having a flexible seal coupled to the moveableplunger to seal the fluid chamber and the expandable gas chamber. Thefirst movable plunger may form a common wall between the expandable gaschamber and the fluid chamber. Hence, a first movable plunger may beformed of a first movable structure or wall, and a second movableplunger may be formed of a second moveable structure forming a secondwall of the expandable gas chamber. Removal of the gas from theexpandable gas chamber moves the second moveable structure to collapsethe expandable gas chamber. Other embodiments may be implemented withfewer or more structural components or functional parts.

The electronic controller may be configured to operate a gas releasevalve, which may take the form of the solenoid valve or piezo valvedescribed above. Thus, the electronic controller can release gas fromthe expandable gas chamber in response to the amount of fluid beingdispensed from the fluid chamber either automatically or under usercontrol.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that the described feature,operation, structure, or characteristic may be implemented in at leastone embodiment. Thus, the phrases “in one embodiment,” “in anembodiment,” and similar phrases throughout this specification may, butdo not necessarily, refer to the same embodiment.

Furthermore, the described features, operations, structures, orcharacteristics of the described embodiments may be combined in anysuitable manner. Hence, the numerous details provided here, such asexamples of electrode configurations, housing configurations, chamberconfigurations, and so forth, provide an understanding of severalembodiments of methods of dispensing a fluid and on-demand fluiddispensers. However, some embodiments may be practiced without one ormore of the specific details, or with other features operations,components, materials, and so forth. In other instances, well-knownstructures, materials, or operations are not shown or described in atleast some of the figures for the sake of brevity and clarity.

Although specific embodiments have been described and illustrated, theinvention is not to be limited to the specific forms or arrangements ofparts so described and illustrated. The scope of the invention is to bedefined by the claims appended hereto and their equivalents.

1. An on-demand fluid dispenser comprising: an expandable gas chambercomprising a first moveable structure forming a first wall of theexpandable gas chamber and moving along a linear path, the firstmoveable structure comprising a first mechanism to inhibit movement ofthe first moveable structure in a backward direction along the linearpath; a second moveable structure forming a second wall of theexpandable gas chamber and moving along the linear path, the secondmoveable structure comprising a second mechanism to inhibit movement ofthe second moveable structure in the backward direction along the linearpath; a fluid chamber, wherein the first moveable structure forms a wallof the fluid chamber; and an on-demand gas cell to generate a gas ondemand and to direct the gas to the expandable gas chamber to expand theexpandable gas chamber, wherein expansion of the expandable gas chambermoves the first moveable structure in a forward direction along thelinear path to reduce a volume of the fluid chamber and to dispense anamount of fluid from the fluid chamber, and contraction of theexpandable gas chamber moves the second moveable structure in theforward direction along the linear path.
 2. The on-demand fluiddispenser of claim 1, further comprising: a power source connected tothe on-demand gas cell; and a switch coupled to the power source, theswitch configured to activate the on-demand gas cell, wherein theon-demand gas cell is configured to produce a volume of gas in a rangefrom about twenty to fifty microliters in approximately three seconds.3. The on-demand fluid dispenser of claim 1, further comprising a gaspermeable element forming at least a portion of a wall of the expandablegas chamber, wherein the gas permeates out of the expandable gas chamberthrough the gas permeable element.
 4. The on-demand fluid dispenser ofclaim 1, further comprising a solenoid valve coupled to a wall of theexpandable gas chamber, wherein the solenoid valve is configured to opento release the gas from the expandable gas chamber.
 5. The on-demandfluid dispenser of claim 1, further comprising a pump coupled to theexpandable gas chamber, wherein the pump is configured to pump the gasout of the expandable gas chamber to contract the expandable gaschamber.
 6. The on-demand fluid dispenser of claim 1, wherein theon-demand gas cell moves with the second moveable structure.
 7. Theon-demand fluid dispenser of claim 6, further comprising: an outletcoupled to the fluid chamber to dispense the fluid from the fluidchamber; and a valve coupled to the outlet to inhibit a flow of fluidback into the fluid chamber.
 8. The on-demand fluid dispenser of claim6, wherein the on-demand gas cell is physically coupled to the secondmoveable structure.